Aquatic Zoos - Captive Animals Protection Society

Sometimes some species may be housed with others because they either look similar, or in the visitor’s
mind they might be living together in the wild, when in reality they never would find each other in their
respective natural habitats. For instance, most Banggai cardinalfish in public and private aquaria (figure
47) are commonly kept with coral reef species, despite the fact that they live in seagrass beds miles
away from coral reefs (Delbeck, 1999). This, although does not necessarily mean that these fish may
suffer from the presence of its unusual companions, does not help public aquaria to fulfil their selfimposed
education role, which should have being considered when designing their exhibits.
Figure 47. Banggai cardinal fish kept in a UK public aquarium tank together with
tropical reef fish species that never would encounter it in the wild.
Although it may seem impossible, sometimes the design of exhibits does not prevent animals in aquaria
from escaping their tanks. In one UK public aquaria in the year 2000 a shark leapt out of its tank twice
and landed among visitors (Anonymous, 2000), and the low walls of the tanks were blamed for the
event.
The materials used in the exhibits or even the chemical procedures to treat the water may also be
chosen wrongly as part of a public aquarium design. Aluminium is acutely toxic to fish and invertebrates,
so it should not be used in the design of tanks. Synthetic salts that may be used in public aquaria are
notorious for containing elevated levels of this element due to impurities (Poléo, 1995).
In fact, metals should not be part of the submerged portion of a tank when species sensitive to electric
fields are housed. In Steinhart aquarium (San Francisco) a young great white shark that was held in a
doughnut-shape tank kept crashing into the wall at the exact spot, and it turned out that some corroded
metal was generating a weak electric current (Bright, 1999).
Ozone is commonly used to disinfect the water of public aquarium systems but it is a powerful oxidant
and can elevate ‘Oxidation Reduction Potential’ (ORP) values to unsafe levels. Several sharks deaths in
UK public aquaria have been blamed on this, not only in published cases (Anonymous, 2001a), but also
in unpublished ones.
Although it is very difficult to measure the actual free volume a shark may have in an aquarium without
having exact measures of its tank (visual references are not good enough to assess size in aquaria due
to the distortion water refraction produces), or to know the actual composition of the aquarium artificial
salt, some display designs can indeed be assessed through a simple visit to the aquarium. In this chapter
we will pay attention to some of them.
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